First let me preface this with the disclaimer that the only things I know about babies are that they smell really good and that holding them is better than reading a good book.
I ran across this recipe while looking for ways to prepare beef heart and thought of this thread. Hope it helps.
Poached Beef Heart Baby Food
2 cups sodium-free beef or chicken stock
1 pound beef heart, trimmed and cut into 1 inch cubes
1 clove garlic, sliced
Pinch of salt (optional)
Over high heat, bring the stock to a boil in a medium saute pan. Add the beef heart and enough cool water to submerge the pieces. Briefly return the liquid to a boil then lower the heat to maintain a gentle simmer. Add the optional garlic; cover the pan with a lid.
Poach on the stove for 30 minutes or until the pieces are completely tender and easily pierced with a knife. Remove the beef heart from the stock, reserving both separately and cooling for 10 minutes.
Add the cooked beef heart, 1/2 cup of stock and a pinch of salt to a large blender or food processor. Carefully blend into a smooth puree, adding more cooled stock as necessary to achieve the desired consistency. If you accidentally overshoot on the stock and the puree becomes watery, add boiled sweet potato, overcooked pasta, or powdered brown rice cereal to thicken it again. (Reserve any remaining stock for soups, stews, or to rehydrate legumes.) And if you desire an even smoother consistency, push the puree through a fine mesh sieve discarding any lumpy solids left behind.
Decant the baby food into a clean bowl and cover the surface with plastic wrap. Once cooled to a "baby appropriate" temperature, serve in generous portions to your adventurous eater.
Extra puree can be poured into ice cube trays, covered, and stored in the freezer for up to 3 months.
Source: Beef Heart: An Unexpected Meal That Spans Generations : The Salt : NPR
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